Weather for Boaters

Weather: The #1 Factor in Boating Safety

More boats are lost to bad weather than any other cause. Wind, waves, lightning, fog, and storms don’t care about your experience level or boat size. The difference between competent and incompetent boaters isn’t avoiding weather—it’s understanding weather, planning around it, and knowing when to stay at the dock.

Weather forecasting for boaters isn’t about being a meteorologist. It’s about accessing reliable forecasts, interpreting what they mean for your specific waters, and making conservative go/no-go decisions before conditions deteriorate.

Marine Weather Forecasts vs General Weather

Don’t rely on general weather apps designed for land. Marine forecasts provide critical information general forecasts omit:

• Wind speed and direction: Sustained winds and gusts in knots
• Wave height and period: How big and how frequent
• Sea state: Seas, swells, and combined conditions
• Visibility: Fog, rain, and haze forecasts
• Warnings: Small craft advisories, gale warnings, storm warnings

Understanding Marine Forecasts

Wind is reported as sustained speed (average over 2 minutes) and gusts (brief peaks). “West wind 15-20 knots with gusts to 25” means average winds from the west at 15-20 knots, occasionally spiking to 25.

Remember: Wind direction is where wind comes FROM. A west wind blows from west to east. This confuses many beginners since current direction is stated as where it flows TO.

Seas are wind-driven waves in the immediate area. Swells are waves from distant storms that travel hundreds of miles. Forecasts often separate them: “Seas 2-3 feet, southwest swell 4-6 feet at 10 seconds.”

Wave period is the time between wave crests (in seconds). Long-period swells (10+ seconds) are manageable. Short-period seas (4-6 seconds) are steep, choppy, and uncomfortable. A 4-foot wave at 5 seconds is much worse than a 6-foot wave at 12 seconds.

Combined seas add seas and swells together. “Combined seas 6-8 feet” means total wave heights from all sources. Always pay attention to combined seas—multiple swells from different directions create confused, unpredictable conditions.

Marine Weather Warning System

The National Weather Service issues standardized warnings for mariners:

Small Craft Advisory: Sustained winds 20-33 knots or seas 7+ feet. “Small craft” means boats under 65 feet, but even large recreational boats should take these seriously. If you have to ask whether your boat qualifies, stay in.

Gale Warning: Sustained winds 34-47 knots. Recreational boats should be in protected harbors, period.

Storm Warning: Sustained winds 48-63 knots. Life-threatening conditions even for large vessels.

Hurricane Warning: Sustained winds 64+ knots. Secure your boat and evacuate.

Special Marine Warning: Sudden dangerous conditions (thunderstorms, waterspouts, etc.) expected within the hour. Seek shelter immediately.

Where to Get Marine Weather

VHF Weather Radio (WX Channels)
NOAA broadcasts continuous weather on dedicated VHF channels (WX1-WX10, usually around 162.4-162.55 MHz). Updated every 3-6 hours, with immediate special statements for sudden changes. This is your primary underway weather source—no internet required.

NOAA Marine Weather Website
marine.weather.gov provides detailed forecasts by zone, including offshore and high seas forecasts. Graphical marine forecasts show wind/wave/weather overlaid on maps.

Windy.com and PredictWind
Visual forecast websites showing animated wind and wave predictions. Excellent for passage planning—you can see how conditions evolve over multiple days.

Buoy Data (NDBC)
Real-time observations from offshore weather buoys at ndbc.noaa.gov. See what’s actually happening right now—wind, waves, pressure, water temperature. If the buoy offshore of your destination is reporting 25 knots and 8-foot seas, that’s what you’ll encounter.

SiriusXM Marine Weather
Subscription satellite weather service providing radar, forecasts, and sea surface temperatures directly to your chartplotter. No internet or cell coverage required. Popular with offshore cruisers.

Reading the Sky: Visual Weather Signs

Forecasts fail. Learn to read actual conditions and predict short-term changes:

Cloud Types:

• Cumulus (puffy fair weather clouds): Stable conditions
• Cumulonimbus (towering thunderheads): Severe weather imminent—lightning, heavy rain, strong gusty winds
• Cirrus (high, wispy clouds): Weather change coming in 12-24 hours
• Stratus (low, gray blanket): Drizzle or light rain, poor visibility

Barometric Pressure:
Falling pressure (dropping 0.02+ inches per hour) means deteriorating weather. Rapidly falling pressure indicates approaching storms. Rising pressure brings improving conditions.

Wind Shifts:
Sudden wind direction changes often precede frontal passages. Wind backing (shifting counterclockwise) suggests a warm front. Wind veering (shifting clockwise) suggests a cold front, often with stronger winds and squalls.

Thunderstorms: The Deadliest Weather Threat

Thunderstorms produce lightning (which kills), microbursts (sudden 60+ knot downbursts), heavy rain (zero visibility), and hail. They form quickly and move fast.

Avoidance: Don’t go out when thunderstorms are forecast. If caught offshore, get as far away as possible. Storms move 15-25 knots—calculate if you can outrun them or if you need to seek protected anchorage.

If Caught in a Storm:

• Get everyone into life jackets immediately
• Close hatches and ports
• Disconnect electronics (lightning protection)
• Stay low in the boat (lightning seeks highest point)
• Don’t touch metal railings or stays
• Head to shore if close; otherwise ride it out away from other boats

Fog Navigation

Fog reduces visibility to near zero, making collision risk extreme. If fog is forecast, stay in. If caught in fog:

• Slow down immediately
• Turn on navigation lights
• Sound fog signals (one long blast every 2 minutes for powerboats)
• Post a lookout to listen for other vessels
• Use radar and GPS, but don’t rely solely on them
• Consider anchoring in safe water until fog clears

Fog often forms when warm, moist air moves over cold water—common in spring and early summer. Radiation fog forms overnight over land and spills onto water at dawn, usually burning off by mid-morning.

Sea Breeze and Local Effects

On sunny days with light overall winds, sea breezes develop as land heats faster than water. Cool air over water flows toward land (sea breeze), strengthening through the afternoon and dying at sunset. Sea breezes can reach 15-20 knots even when the forecast calls for 5-10 knots.

Coastal topography creates local effects—wind funnels through valleys, accelerates around points, and dies in the lee of hills. Local knowledge reveals these patterns. Pay attention and you’ll learn when your waters are calmer or rougher than forecasts suggest.

Making Go/No-Go Decisions

Conservative decisions keep you alive. Ask yourself:

• Are conditions within my boat’s capabilities?
• Are conditions within MY capabilities?
• Is everyone aboard comfortable with this?
• Do I have escape routes if weather worsens?
• Can I return safely if I need to turn back?

Small craft advisories don’t automatically mean “don’t go,” but they do mean “be prepared for difficult conditions.” If you’re new to boating, treat them as hard limits. As you gain experience, you’ll learn your boat’s and your own limits.

The golden rule: If you’re questioning whether to go, don’t go. The water will be there tomorrow. Your boat, your passengers, and your life won’t if you make a bad decision.

Building Weather Awareness

Check marine weather every time you boat, even for short local trips. Compare forecasts to actual conditions and note discrepancies. Keep a weather log recording wind, seas, and barometric pressure. Over time, you’ll develop intuition for how weather behaves in your area.

Weather knowledge isn’t optional—it’s the foundation of safe boating. Respect it, study it, and let it guide your decisions. The best captains aren’t the ones who brave storms; they’re the ones who avoid them.